Specially engineered killer T-cells could make organ rejection a thing of the past">The greatest problem for transplant procedures is that the body's immune system will reject the life-saving replacement organ. But mice have special cells that can selectively suppress the immune response - and they could revolutionize organ transplants for humans.

The immune system in both humans and mice (and most other mammals) is controlled by a type of white blood cells that are awesomely named natural killer T-cells. Although these cells make up less than a fraction of a percent of all white blood cells, recent studies have shown their proper function is hugely important in warding off diseases like diabetes, atherosclerosis, and cancers. And now researchers may have discovered an even more remarkable ability.

A team at Portugal's University of Lisbon studied a particular population of these natural killer T-cells, or NKT cells, and how they operated in mice. This subgroup of NKT cells was apparently charged with suppressing the immune response of regulatory T-cells around the livers of the mice. The researchers isolated some of these cells and removed them from the bloodstream, injecting them with fluorescent markers. When they were injected back into the mice elsewhere in the bloodstream, the cells headed straight back to the liver and went right back to preventing proper immune function.

Although these cells, which the researchers named NKTreg cells, might not be so desirable when the liver is under attack from an outside infection, they're perfect for liver transplants. Right now, donor livers need to be perfectly matched to their transplant recipients, and even then it's a tricky process that can easily lead to the body rejecting the organ. Worse, recipients often need to take immunosuppressant drugs. These stop the body preventing the new organ but also place the recipient at greatly increased risk of infection elsewhere.

These NKTreg cells offer a way to suppress the immune response around the transplanted organ without weakening the rest of the immune system. Humans also possess these NKTreg cells, so this should be a way forward for better liver transplants. As for other types of organ transplants, that will require either repurposing these NKTreg cells so that they target other organs or finding other populations of NKTreg cells that are associated with different organs.